1. Field of the Invention
The present invention relates to a light source apparatus suitable for use in an endoscope.
2. Description of the Related Art
Conventionally, endoscopes are widely used in which an elongated endoscope is inserted into a body cavity or the like to observe a region to be inspected or perform various kinds of treatment. In such endoscopes, a light source apparatus for photographing an interior of the cavity is adopted. In recent years, light source apparatuses may be used which adopt a semiconductor light source such as an LED as a light-emitting section. Such light source apparatuses can perform light adjustment control of the LED through PWM control that changes a duty ratio of drive pulses and current control that changes an LED current.
As an illumination apparatus using such an LED light source, there is an apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2009-192772. The apparatus according to Japanese Patent Application Laid-Open Publication No. 2009-192772 obtains illuminating light by synthesizing light from an LED generating red light, an LED generating green light and an LED generating blue light, provides optical sensors for detecting light amounts of the LEDs of the respective colors and controls drive currents supplied to the respective LEDs so as to reduce differences between the light amounts detected by the respective optical sensors and target light amount values. Thus, the apparatus described in Japanese Patent Application Laid-Open Publication No. 2009-192772 makes it possible to obtain illuminating light with a desired color balance.
Note that each LED has a characteristic which differs depending on the color of light generated, and for example, a maximum amount of light emission differs for each color LED. Moreover, the maximum light amount used of each color LED also differs depending on a, color balance setting. That is, an amount of incident light of each optical sensor differs from one color LED to another.